| Owing to their versatile chemical transformations, alkyl and aryl2,3-unsaturated glycosidesare important chiral intermediates in the synthesis of biologically active molecules and newfunctional materials. Ferrier rearrangement is an efficient and facile reaction for the synthesis of2,3-unsaturated glycopyranosides. A variety of reagents have been used to promote this reaction,including Bronsted acids,Lewis acids, as well as other reagents such as oxidants, etc. Due to theirspecial properties and high catalytic activity, rare earth metal salts as catalyst have recently gainedmore and more applications. Among them, Sc(OTf)3, CeCl3, Dy(OTf)3, Er(OTf)3, and Yb(OTf)3have been reported to be employed as the catalyst in Ferrier Rearrangement.However, some of those reaction systems suffered from the drawbacks in terms of largeexcess of nucleophile, stiochiometric amount of catalyst, harsh reaction conditions, and low yields,which leading to extensive work up. Our continuing effort concentrated on the searchment formore efficient catalyst for Ferrier rearrangement. Here we report our result. In this paper,the greenand efficient Y(OTf)3has been applied to Ferrier rearrangement reaction for the first time1) We found Y(OTf)3is a highly efficient catalyst for the transformation of various glucals to theO-and S-2,3-unsaturated glucosides. By using Y(OTf)3as the catalyst, a series of2,3-unsaturated-glucosides have been synthesized from3,4,6-tri-O-acetyl–D-glucal,3,4-Di-O-acetyl-6-deoxy-L-glucal and3,4,6-tri-O-benzyl–D-glucal under mild reactionconditions in good yield and high anomeric selectivity. It was found that, in this reaction,3,4,6-tri-O-benzyl–D-glucal behaved differently from the other two glucals when it wasreacted with phenol, O-benzyl glucoside instead of O-phenyl glucoside formed as the soleproduct.An explanation is given for this phenomenon.2) We studied the application of ammonium persulfate(APS) as a new non-metal Lewis acid catalyst for Type I Ferrier rearrangement. A series of2,3-unsaturated glycosides with alcohols asnucleophiles were prepared with this catalyst. |
